Flexible fan unit



Aug. 5, 1941.

' a P. LARsH FLEXIBLE FAN UNIT s suena-smet 1 Filed Jima 13, 1938 A0865- l941- E. P. LARsH 2,251,887

umana ma uuu l y Filed June' 1 s, 193s s sheets-shut l2 Aug. 5, 1941. E.P. LARsH FLEXIBLE FAN UNIT Filed June 13, 1938 3 Sheets-Shogi. 5

Patented Aug. 5, 1941 UNITED sTA'ras-p PATEN'iA OFFICE Everett r.AhTslnor to The Master Electric Company,

poration of Ohio Dayton, Ohio, a cor- Applicatlon June 13, 1938,SerialNo. 213,359 18 Claims. (Cl. 17o-'159) This invention pertains toelectric fans. and more particularly to reinforced blades therefor offlexible or pliable material and the method of manufacture thereof.

Use of non-rigid flexible or resilient fan blades to minimize injuryupon contact therewith and to obviate the 4necessity for enclosureguards has been long known. In some. instances these fan elements havebeen pliable or exible straps, connected at their ends, and in othersthe blades are normally limp wings which are distended by centrifugalinfluence during rotation. In stillother embodiments the material of theblades has been impregnated with some stiffening material or the bladeshave been molded from rubber'or other composition in such a way as torender them somewhat'self-supporting or resistant. However, thesedevices have for the most part lacked 4stability and have beenineillcient in use, tending to yield to air resistance and are otherwiseobjectionable.

The present fan vblade structure forming the subject matter hereof isreinforced by a formed metal insert or abbreviated blade of somewhatsmaller size, suitably shaped and contoured, which is embedded in theflexible materialof the blade to afford suilicient rigidity throughoutthe major portion thereof to enable it to retain its prescribed. shapeand inclination or pitch against air resistance, and beyond which themargins and terminal extensions of the blade aresuiliciently flexibleand resilient that they yield to contactv with an interposed obstructionat operating speed.andaresuillcientlyresilienttobeself restoring when sodistorted from normal shape.

The object ofthe invention is to improve the Aconstruction as well asthe mode of operation of A further object of the invention is tominimize noise during operation.

A further object of the invention is to assure retention of a prescribedvshape and pitch of the blade, minimize the necessary amount of rubberor other flexible material, and reduce the weight of the completedimpeller unit.

A further object of the invention is to provide an improved method ofmounting the impeller.

A further object of the invention yis to provide a rotary fan having theherein mentioned advantageous structural features and meritoriouscharacterlstics.

With the above primary and other incidental objects in view as will morefully appear in the specification, the invention intended to beprotected by Letters Patent consists of the features of construction,the parts and combinations'thereof, and the mode of operation, or theirequivae lents. as hereinafter described or illustrated in theaccompanying drawings. i

I'n the drawings, wherein is shown thev preierred but obviously notnecessarily the only form of embodiment of the invention, Fig. 1 is eside elevation of an electric fan equipped with a rotary flexiblerotorjor blade unit embodying the present invention.

Fig. 2 is a front elevation composite rotor or impeller.

Fig. 3 is a side elevation thereof.

Fig. 4 is a transverse sectional view through one of the blades.

Fig. 5 is a front elevation of the petaliform reinforcement insert orcore member.

repair.

A further object of .the invention is to provide a v fan blade havingsufhcient nexibility to prevent injury in event of accidental contact,wherein the deformation is restricted to a limited area withoutdestroying' or materially decreasing the air impelling action oftheblade while'so deformedortemporarilydisturbingitsbalancetoanyappreciable degree. A l

Amrth'erobjectoftheinventionistoincrease the stability of iiexible fanblades and provide a maximum effective air impelling area under allconditions.

Fig.'6 is a side elevation of the reinforcement core before embedment inthe resilient blade ma- Fig. 'I is a radial section through the bladesand hub of the impeller.

Fig. 8 is a front view of one member of a sectional reinforcement core.

Fig. 9 illustrates an economical mode ofblankingthesectionsshowninllg.8.

Fig. l0 is a front elevation ofan assembled sectional core. y

Fig. ll is a sectional view of a'modication..

Fig. 12'is a detail view of a single blade element.

of reference throughout the several views.

In the drawings, l indicates'. eonvenuonsl pedestal and motorhousing'ofaportable elecof the assembled v Pitch angle at all times.

tric ian, the particular shape and detail construction of which are notmaterial to the present invention. Mounted on the motor shaft is theameter oi the motor shaft on which the impeller composite impeller orblade unit 2 forming the subject matter hereof. For illustrativepurposes the impeller is shown as comprisingv a group of four radiallydisposed, internally reinforced blades 3.-3. The number of blades andthe particular shape thereof may be varied to accommodate the fan todifferent operating conditions and requirements. The major bodies of theblades 3 may be formed of any suitable pliable or resilient materialsuch as paper, fabric,flber, or the like, but are preferably molded fromsoft or semi-soft rubber. While the several blades 3 may beindependently formed and subsequently assembled into the'unitaryimpeller 2, the blade'assembly is preferably formed as a single integralunit.v

Embedded in the impeller is ametallic reinforcement core t or insertshown in Figs. `5 and 6, stamped or otherwise formed from sheet metal.The core. orinsert licomprises a plurality of integrally interconnectedradially ldisposed leaves of obovate form, which may .be well termed apetaliform insert or core. The fan blades 4,' including the Ileaves orpetals of such petaliform insert,'emb`edded therein are transverselycurved or of ooncavo-convex form. In addition to such curvature they areinclined to the common plane of rotation, thus aEording a pitch anglecom-I mensurate with the desiredair impelling action.

or ian. bladeunit is to be mounted. A4 group oi' additional holes 8 arealso provided in diie'rent radial positions about the central shaft hole1,

the size o, which is also reduced'in like manner holes 'i and 8 providesa flexible; somewhat resilient mounting for the rotor unit which absorbsvibration and minimizes noise. It further enables therrotor -toautomatically adjust itself f within reasonable limits into the plane ofrota-.-

Y tion if it should become inclined thereto.

Adjacent to the inner ends of the bladesat which they are joined to eachother, the leaves or petals of the petaliforminsert are interconnectedby a disc like hub portion. The contigf nous portions yof thereinforcement leaves are embossed to afford stiiening beads or ribs 5.

For illustrative purpose the stiilening beads or ribs have been shown asof arcuate form grouped in spaced relation about the center of the coreor insert. They may, however, be otherwise disposed in such relation aswill best meet the requirements and conditions of use to which theimpeller is to be subjected. Such construction andconiiguration rendersthe blades ot the im` peller suiilciently rigid to maintain itseffective The embossed ribs or beads Salso serve to materiallystrengthen the impeller blades at their otherwise weakest points, i. e.,their juncture with the hub, to prevent breakage or bending of of theinsert.

The rubber or other flexible covering` of the insert may be applied inany suitable manner or customary way. Ordinarily this is performed in a'suitable mold under heat. and pressure. It is, however, 'highlyimportant that each of the fan blades shall contain equal amounts ofmaterial and that the petaliforminsert or vcore shall be symmetricallylocated. toafford a properly balnelly-and transversely. are greater thanthosev The tips of the bladesextend al considerable distance beyond thetermini of the insert leaves as shown by solid and dotted lines in Fig.2. Likewise the leading and'trailing edges of the blades extend beyondthe edges of the reinforcement insert. Such extended portions aresufficiently flexible to yield 'under impact and permit the lextensionsof the blades to bend withoutbreakage or permanent distortion. Suchportions are suiliciently resilient and possess with a series oftransverse ribsv 9 of low altitude. as compared with their width. Theribs or beads 9 are of curvilinear form concentric withk the the bladesout of their common plane or rotation. I

-To aiord increased anchorage of the rubber or other iiexible or pliablematerial of which the blade is formed and in which the petaliform coreor insert is embedded, the latter is'provided with a series oi holes 66, through which the mateerial at opposite sides ofthe insert isintegrally united. These are shown as transverse sl'ots,. but

may be otherwise shaped,and may comprise a series of spaced round orirregular holes or elonp gated slots otherwise disposed in each leaf orpetal of the unitary insert.' I

At its center the insert is provided with a hole 1, preferably,lalthough not necessarily, largerl than the diameter of the shaft onwhich the impeller is to be mounted.

During the subsequent embedding operation.v

in which a body of flexible or resilient material is molded or otherwiseformed about. the insert,

Athe rubber or other enclosing material partially illls such hole 1,uniting through the hole the enclosing material at opposite side of theinsert for increased security and thereby reducing the size of the holeto somewhat less than the diaxis of the rotor or impeller.

"coincident with the center of the unitthere` is formed a projectingconoidal hub l0 having` therein an axial bore and a series of relativelyspaced bores parallel thereto coincident with the holes l and d of theinsert. The hub l0 is'integother exible body while. dat and the bladessubsequently shaped tothe proper curvature and pitch inclination.However, the preferable method is to contour the insert leaves to theirnnal shape before embedment and thereafter mold the rubber or likematerial thereabout into f agreement with the bladesor leaves of thepreformed insert.

By such construction strains and stresses in the rubber cover as welllas in the insert are' avoided and the material may be more uniformly,

distributed.y The extensions vof the' rubber blades beyond the limits ofthe insert, as indicated in Fig. 2, provides flexible terminals and alsoexible leading and trailing edges which extend cn-YV siderable distancesbeyond the perlpheries of petal or leaf sections of. the insert andwhich will yield upon impact engagement with an object without injury toeither the blade o! the object and -will resume their original shapeswhen free therefrom. The provision of the reinforcementinsertandtheofthecentralportion thereof affords such construction andconfiguration as to maintain the pitch angle'and concavoconvex contourof the fan blades under all conditions. integral'component of the finalimpeller structure and an inherent part of each blade thereof,

The reinforcement insert becomes anf like, such yielding effect of onereinforced blade rendering the blades self-supporting and amply rigidthroughout the inner radial portions thereof to perform their airimpelling functions while' core member in the mold in symmetricalrelation therewith while the rubber is being molded there# about. Therubber mold is -provided interiorly with a group of studs correspondingto the studs I3 which in the finished product afford the spaced bores8', and over which the reinforcement core is positioned with suchlocating studs engaging -in tne holes 8 thereof. Such locating use isadaditional to the driving function of the-holes. In the event that theimpeller is' of smallsize or not subject to great load, it may befrictionally engaged upon the drive shaft l2 by merely press- Y ing tneshaft into the central bore 1 without use of driving studs I8 to engagethe bores 8. I'he bore l being of somewhat smaller diameter than that ofthe shaft, the contiguous rubber material is subjected to expansivetension causing the shaft to vbe firmly gripped by the rubber hub.

While the reinforcement core is illustrated and described as comprisingmultiple integrally interconnected leaves, it maybe assembled fromseparately formed elements consisting initially of either single ordouble leaf elements united by welding or riveting or otherwise, or suchindependent reinforcement elements or inserts may be separatelyembeddedin the enclosing body of rubber and flexibly inter-connected bythe con-l tiguous portions of rubber. v

The single integral reinforcement insert I having'integral radiallydisposed leaves cannot be blanked from the sheet material without con#-4siderable waste. However, if the reinforcement insert leaves are formedin pairs as Vsliown'in Fig. 8, they may be more y'blankedilwithminimumwasteof would not be subject to the fullflmonientum orinertia of the impeller. Such commotion would possess a'slight shockabsorbent characteristic under such circumstances. By supporting two ofthe separately formed units in the rubber mold in slightly spacedrelation with each other and embedding them in a single body of rubberor the relativey to another may be achieved. In Fig. 11 such relation ofseparate reinforcement or insert elements flexibly connected isillustrated. If so desired, each reinforcement leaf may be separatelyformed and indeed separately embedded in v rubber for assembly side byside on a drive shaft.

In Fig. 12 there is shown one such single reinforced flexible bladeelement, and in Fig. 13 a f series of such individual flexiblereinforced blades .are shown assembled in cooperative relation on adrive shaft. Such assembly may consist of two,

three or any greater number of blade elements. Such members agreegenerally in form and construction with those previously described,-including a simlar insert leaf l and integral hub portion embedded m aflexible rubber feit or com. i

position blade of greater size, including a rubber hub portion.

From the above description it will he apparent that there is thusprovided a device of the character described possessing the particularfeatures of advantage before enumerated as desirable, but whichobviously is.v susceptible of modification in its form, proportions,detail construction and ar-` rangement of parts without departing fromthe principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has beendescribed in language more or less specific as to structural features,it is to -be understood that the invention is not limited to the specicfeatures shown, but that the means and construction herein disclosedcomprise the preferred form of severall modes of putting the inventionintoreiect, and the invention is therefore claimed in any of its formsor modiiications within the legitimate and valid scope of the appendedclaims.

Having thus described my invention,I claim:

1. A fan element including' a hub portion and ,a plurality of integrallyunited blades molded to shape from rubber, a unitary metallic petaliformcore member of sheet metal reinforcing the hub and inner radial end onlyof each blade.' 'the outer radial portion of each blade being free fromany reinforcement and being sufficiently soft andinFig.lilandunitedbyxveldingorbyrlveting.k

In lieu thereof itis quitepractical and desirtvetoeachother. 'lhisis foruse under conditi@ where fingen may beintothepathofrot'atlonoftheblades.Uponcontactwithanintereeptingnngerorother flexible to yield uponengagement with an object and having capacity toresumeits shape whenfree from the object..

2. A fan element presenting a petaliform core portion of sheet metal andrubber covering the core member'andextendlng radially lybeyondtheperipheryofeachofthepetalsections of the core member, thereby'providing a' rubber fan in which each blade is interior-ly reinforced atits inner radial end and the outer radial portion ofwhlch is soft andflexible.

3.a fan element having a petallformucore portion of sheet material andrubber enclosing eachpetaisectionofthecoreportinntoform the'blades ofthefan and'also enclosing the central part of the core said yrubber havingconsiderable thickness unid-centrar partofthecorethaebytoformarubberhubforyliae fan, the rumerportion ofAeach blade radially considerablyvbeyond the peextending mmebladewnd'slightlyyieldand isripheryofitspetalsectlonof the core to provide `ber portion of eachblade'extending radially considerably beyond fthe periphery of its petalsec tion of .the core to provide an outer radial por--k tion for theblade which is sumciently exible to yieldwhen it engages an object butwhich is capable of resuming its normal shape when free from saidobject, said rubber hub portion of the fan element having an axialshaft-receiving Opening.

5. A fan element comprising' a hub and blades formed of rubber and apetaliform core member of sheet material embedded in and entirelyenclosed by the rubber with av petal section of said core located atandreinforcing the inner radial end only of each blade, the outer radialportion of each blade being'freev from reinforcement and beingself-sustaining but sumciently flexible to yield when engaged by anobject and capable of i resuming its normal shape when free fromsaidobject.

6. A fan element presenting a petallforrn core portion of sheet metal,the petal sections of which have va. pitch angle corresponding to thepitch angle required in each blade of the fan and an integral rubberportion which covers the core portion and forms both a rubber hub forthe ian and the blades thereof, the rubber part of each blade extendingradially considerably beyond the periphery. of the petal section.thereot and normally having a less pitch angle than that of thecorresponding petal section, the rubber portion of each blade being heldin distorted condition at said required pitch angle of the blade bythecorresponding petal section of the core, the outer radial portion ofeach blade beingvsumciently flexible to yield when it engages an objectbut being capable of resuming its normal Shape when iree from saidobject.

7. A fan comprising a hub, radially projecting` blades carried thereby,and a petaliform reinforcement insert embedded interiorly thereof. saidblades being formed at their outer portions of material snmcientlyexible to ,bend readily without permanentjdistortion, and the inner end-thrusts Without materially increasing their re= 'sistance todeformation upon encountering an Aao object in' their path of rotation.

10. In a fan, a hub, a plurality ber blades, and a petalifonnreinforcement means embedded'interiorly thereof and coacting with saidhub and base portions of said blades to maintain said blades ina'self-sustained radial position on said 'hub oblique to the axis ofrotation, said blades being sufiiciently iiexible and resilient tobe-self-restoring after striking an object in its path of rotation andoi sufilcient rigidity to substantially maintain a pitch angle uponrotation effective for air delivery.

11. In a fan, a hub, rubber blades, and a petaliform reinforcementmember embedded within and engaging portions of said blades formaintaining them in a normally radial and substantially cupped positionon said hub, said blades being of such flexibility and resilience as tobe self-restoring upon distortion from normal position and of suilicientrigidity when assembled to substantially maintain a predetermined pitchposition on the hub.

[12. A fan comprising a hub, radially project-4 ing blades carriedthereby, said blades being formed of material suciently flexible tobendreadily Without permanent distortion, and a .petaliform reinforcingmember embedded in the inner end portions of said blades of aconstruction and configuration such that said blades are sufficientlyrigid to substantially maintain their pitch angle upon rotation, andsaid blades being relatively wide with respect to their radialdimension. A l

13. A fan comprising a hub, radially projecting blades carried thereby,said blades being formed of a. material sufficiently iiexible. to bendreadily vupon striking an object without permanent dis-v tortion, and 'apetaliform reinforcing element embedded in the inner end portions ofsaid blades,

' of a construction and configuration such that Portions of said bladesbeing' of a construction andconguration such that said blades aresumciently rigid to maintain a substantially radial position at alltimes.`

8. A fan comprising a hub, radially projecting blades carried thereby,and a petaliform reinforcement insert embedded interiorly thereof, saidblades being formed at their outer portions of material suillcientlyflexible to bend readily withoutl permanent distortion, and the innerend portions of said blades being of an obliquely curved configurationand a construction such that said blades are 'suciently rigid tomaintain an eifective pitch angle upon rotation.

9. A fan comprising a hub, radiallyproiecting blades formed of materialsufficiently flexible to bendreadily without permanent distortionpand apetaliform reinforcement of less extent than the V`blades embeddedinteriorly thereof, the inner end portions of said blades beingmaintained sunlciently rigid by said hub and of a configuration toincrease the resistance of said blades to axial said blades aresuiciently rigid to maintain an effective pitch angle at all times.

14. A rotary fan impeller including a plurality of radiallydisposed'blades of flexible material and a centrally disposed conoidalhub thereforof like material formed integrally with the flexiblematerial of the blades, and a unitary reinforcement insert comprisingmultiple interconnected radially disposed leaves of strain resistantmaterial, one leaf of which is ,embedded in each blade thereof of theimpeller and a central portion of the insert integrally connecting theleaves one with another and embedded `in the conoidal hub of the.impeller, said hub and insert havingtions fixedly interconnected witheach other and I a rubber covering in which the reinforcement coreassembly 'is embedded, said covering extending beyond the periphery ofeach vsection of the core, thereby providing a fan elementin which eachblade is interiorly reinforced at its inner radial end and the oiiterradial portion of which is soft and flexible. A

16.v A fan element including a petaliform reinforcement core comprisingplural separate sections' andA a rubber covering in which the reinyforcement-core sections are. embedded and by which they are yieldinglyconnected with each other, said covering extending beyond the periphery.of each section of the core lthereby probl, and a hub portibn upon eachblade by whichviding a Ian element in which i,he` bladesare. in-yteriorly reinforced at their inner radial ends and the outer portions ofwhich are soft and flexible, the blades being yielding in relation oneto another in the plane of rotation.

17. A fan element including -plural separate reinforcement core sectionsdisposed in petaliform relation, a rubber covering in which each coresection is embedded, said. covering extending beyond the periphery ofthe enclosed reinforcement core section thereby providing a plurality ofseparate fan blades each of which is interiorly reinforced at its innerradial end and the outer radial portion of which is soft'and ilexitheblades may be assembled in radiating relation side by side on a commonshaft.

13.y As an article of. manufacture, a reinforcementinsert for al rubberfan element, comprising a single integral petaliform member formed fromsheet material including a plurality of radially disposed leaves and acentral interconnecting hub portion and a, plurality of spaced locatingholes in said member for engagement of locating studs for positioningthe'insert in a niold to. receive a body of embedding material andeembossed areas on the member to stiien such portions thereof. EVEREI'I'P. LARSH.

